Study of the oscillatory flow of a yield-stress fluid in a cylindrical pipe

Abstract

During this work we studied the oscillatory pipe flow of a Carbopol mixture. The velocity profiles show the non-linearity of the shear stress and the shear rate relation. For low frequencies the viscosity is high and the flow is plug-like. On the contrary, for high frequencies the force made by the piston is high enough to lower the viscosity value and induce a viscous fluid behaviour, leading to a Poiseuille-like profile. We also studied the rheological properties of samples of different concentrations and estimated the value of the yield stress, the consistency index and the flow index fitting the flow ramps to a Herschel-Bulkley-type equation